Evaporator-blower unit for refrigerated equipment



EVAPGRATOR-BLOWER UNT FR REFRIG- ERATED EQUIPMENT Wayne H. Detwiier, Philadelphia, Pa., assigner to C. V. Hrli t Company, inc., Trenton, NJ., a corporation of New Jersey Application February 26, 1958, Serial No. 7 17,716

2 Claims. (Cl. 62426) This invention relates to refrigeration equipment and is directed particularly to evaporator-blower assemblies adapted to be used for circulating and reducing the temperature of the air in such equipment, and to methods of using such assemblies.

it has been common practice heretofore to cause air to be refrigerated by forcing it over the coils of an evaporator by means of a blower. The coils are ordinarily provided with tins which extend generally parallel to the direction of flow of the air whereby the heat exchange area of the coils exposed to the air is greatly increased but little obstruction is presented to the ow of the air. The eciency of the heat exchange between the air and the coils and tins of the evaporator is materially increased by creating turbulence in the air so that streamlining is avoided and intimate contact between the air and the surfaces of the evaporator is established. It has therefore been usual to place the blower in advance of the evaporator so that the air being presented to the coils and tins is rendered turbulent and more effective cooling thereof is accomplished. However, if the air being circulated is at a temperature below freezing, frost is deposited on the coils and fins of the evaporator and upon continued operation it often is deposited on the blower and its housing to such an extent as to interfere with the operation of the blower.

Frosting of the blower and its housing is reduced or eliminated if the blower is located beyond the evaporator so as to draw the air over the coils and lins thereof. However, the efficiency of heat exchange is thereby reduced in the latter portion of the evaporator by reason of the streamlining action of the fins in reducing the turbulence of the air flowing over the evaporator.

- When using either arrangement of the blower with respect to the evaporator, the fins on the coils must be spaced sufficiently far apart to avoid clogging of the evaporator bythe build up of frost on the fins. Ordinarily the tins are spaced about one half inch or more apart but such spacing of the tins serves to limit the heat exchange area of the evaporator and reduces the eflciency of the heat exchange contact between the air and the fins.

in accordance with the present invention, these objections to constructions of the prior art are overcome and an evaporator-blower assembly is provided which substantially increases the efficiency of operation and heat exchange between the air and the evaporator while avoiding frosting of the blower and its housing.

These results are preferably attained by providing an assembly wherein a portion of the evaporator is located in advance of the blower in a position to collect frost and reduce the moisture content of the air being circulated prior to its contact with the blower and its housing, where- 2,929,229 Patented Mar. 22, 1950 apart a suitable distance to prevent clogging thereof by the accumulation of frost thereon, whereas the ns applied to the coils of the evaporator following the blower may be positioned relatively close together since there is little or no danger of the accumulation of sufficient frost thereon to obstruct the ow of air. The closely spaced tins on the latter portion of the evaporator and the turbulence imparted to the air by the blower combine to assure greatly increased efficiency of heat exchange during the flow of the air over the latter portion of the evaporator. As a result, it is possible to obtain a substantially greater reduction in temperature of the air leaving the assembly without an increase in the size of the evaporator or the load on the refrigerating elements.

The relatively close spacing of the fins on the latter portion of the evaporator also serves to reduce the turbulence of the air leaving the assembly with the result that the air diffusing and distributing members heretofore required in many types of. refrigeration equipment may be eliminated. Moreover, the absorption of heat from surfaces over which the refrigerated air passes on leaving the assembly is reduced by the streamlined iiow thereof so that losses of heat through the walls of the equipment are reduced.

The evaporator and blower elements of the present invention are preferably arranged and supported in a single unit adapted to be located in various types of refrigeration equipment. It is therefore possible to produce a standard evaporator-blower assembly unit adapted to be used in a great variety of different types of equipment.

' Accordingly, the principal objects of the present invention are to increase the efficiency of operation of evaporators employed in refrigeration systems and to reduce the ditliculties heretofore encountered by the accumulation of frost on the evaporator and on the blower and its housing.

A further object of the invention is to provide an evaporator-blower assembly wherein a portion of the evaporator is located in advance of the blower whereas another portion of the evaporator is located at the rear thereof in positionvto receive turbulent but relatively dry air from the blower.

Another object of the invention is to subject air being refrigerated to successive treatments to reduce the moisture content thereof and thereafter to increase the turbulence of the air and pass it over evaporator coils having relatively closely spaced fins thereon which serve to increase the refrigerating eiciency of the evaporator and cause the air to leave the evaporator in a relatively nonturbulent condition.

A particular object of the invention is to provide an evaporator-blower assembly in the form of a unit adapted to be employed in various types of refrigeration equipment.

These and other objects and features of the present invention will appear from the following description thereof in which reference is made to the figures of the accompanying drawing.

In the drawing:

Fig. 1 is a perspective illustrating a typical form of evaporator-blower unit embodying the present invention;

Fig. 2 is a vertical sectional view through the unit illustrated in Fig. 1;

Fig. 3 is a Vertical sectional view through a self-service refrigerated display case embodying the unit of Pigs. l and 2; and

Fig. 4 is a diagrammatic vertical sectional view of a walk-in cooler embodying the unit of Figs. 1 and 2.

. In that form of the invention chosen for purposes of illustration in Figs. 1 and 2, the evaporator-blower assems bly embodies a cas-ing including end plates 2 and 4 and top and bottom plates indicated at 6 and 8 respectively. The casing thus serves to define an air passage having an inlet 10 at one side of the casing and an outlet 12 at the other side thereof. A first evaporator section 14 is located in the air passage adjacent the air inlet 1t) and a second evaporator portion 16 is located in the passage adjacent the air outlet 12. A blower 1S is also located in the air passage of the unit between the evaporator portions 14 land 16 in position to draw air over the rst portion `and force it over the second portion of the evaporator. Both portions of the. evaporator preferably embody coils or tubes through which the refrigerant is circulated andthe tubes have ns applied thereto and spaced apart a suitable distance to permit free flow of air l by the blower and accordingly is very turbulent so that through the air passage of the unit. The tubes E@ of the first evaporator portion 12 are thus provided with fins 22 which, in a typical installation, may be spaced apart one-third to one-half inch or any other suitable distance to provide the maximum heat exchange area without danger of clogging the air passage by accumulation of frost thereon.

The second portion 14 of the evaporator may be similarly constructed with a plurality of refrigerant tubes 24 having tins 26 thereon. However, the tins 26 on tubes 24 are preferably positioned ,relatively close together and need be no more than oneeighth to onequarter of an inch apart.

The blower 18 located between the first and second portions of the evaporator is shown as bein-g in the form of a fan having lblades 26 driven by a motor 28. Any suitable number of blowers may be located in the passage between the first and second portions of the evaporator to insure-substantially uniform flow of air through the unit and over the coils and tins there-of. 18 are mounted on a plate 30 which extends across the space between the evaporator portions 14 and 16 and is spaced between and generally parallel to the top and bottom plates 6 and 8 of the unit. A baie 32 extends from the bottom plate 8 upward to the fan supporting plate 30 leaving a space 34 through which air may flow from the first evaporator portion 14 to the blower 18. In a similar Way, a bafe member 36 extends downward from the top plate 6 of the assembly adjacent the second evaporator portion 16 so as to provide a passage 38 through which air may flow from the blower to the latter portion of the evaporator. The air forced over the portion 16 of the evaporator issues from the unit through the outlet 12.

In 4operating the un-it described, the refrigerant preferably is passed first through the tubes 24 of the second portion of the evaporator and thereafter is passed through the tubes 20 of the rst portion of the evaporator. However, the direction of circulation of the refrigerant through the successive portions of the: evaporator can be reversed if desired and if preferred, each portion of the evaporator may be supplied with refrigerant from a separate source.

Upon actuating the blower 18, air enters the inlet l() of the unit and first comes into Contact with the coils `and fins of the rst evaporator portion 14 by which it is` cooled to a temperature below its dew point. A substantial portion of the moisture carried by the air is thereupon deposited on the coils and fins of the rst portion of the evaporator. The evaporator usually is maintained at a temperature low` enough tol cause the moisture thus condensedto be converted into frost. The heat absorbed by the first portion of the evaporator is therefore largely latent heat extracted from the moisture contained in the air and the temperature of the air itself is not necessarily reduced very greatly. The iirst portion 14 of the evaporator thus is, in eiect, a frost collecting or latent heat absorbing portion.

Ordinarily the airV entering the unit is drawn from the' equipment being refrigerated andis sufficiently turbulent The fans j on passing over the coils and lins of the second portion 16 of the evaporator, intimate contact between the air and the coils and iins is assured. Moreover, the relatively large surface of the closely positioned fins 26 of the portion 16 of the evaporator, in combination with the extreme turbulence imparted to the air by the blower, serves to increase the eiiiciency of the heat exchange of the portion 16 considerably. The air, in passing over the second portion of the evaporator, has its temperature reduced considerablyand, therefore, the portion 16 of the evaporator may be considered a high efficiency temperature reducing evaporator.

The close positioning of the ns 26 on the tubes 24 of the portion 16 of the evaporator serves to suppress turbulence of the air created by the blower and results in streamlining of the a-ir as it leaves the outlet 12 of the unit. The highly refrigerated air leaving the unit therefore can be passed through the equipment to be refrigerated adjacent the walls thereof in a manner to reduce the absorption of heat from the walls or surfaces over which it dows. the air thus developed renders it possible to omit the usuali air diffusing and distributing members heretofore requiredforestablishing uniform circulation of the refrigor-ated air through the equipment.

A typical application of the unit shown in Figs. I and- 2v and described above is illustrated in Fig. 3 wherein the unit is employed for refrigerating and circulating air in a self-service display case which is open at the top for access to customers. In this application of the invention, the case is shown as having an insulated bottom 4d and insulated front and rear walls 42 and 44 respectively. The ends 46 of the case are also insulated and cooperate with the bottom and front and rear walls to form a display space which is open at the top so that customers may reach in and remove articles on disnlazr.

The unit of-Figs. l and 2 is indicated at 48 and is located Vadjacent the bottom 40 of the case beneath an article supporting rack 50 and preferably extends substantially the full length, of the case. The inlet side 10 of unit, 48, communicates with the lower end of a return air duct 52 located adjacent the rear Wall 44 of the case, whereas the upper end of the duct 52 is in position to draw off air from the upper portion of the display space. In a similar way the outlet side 12 of the unit 48 communicates with a cold air duct S4 which extends upwardly adjacent `the front wall 42 of the case and is arranged to discharge refrigerated air into the upper portion of the display space near the top thereof. The portions 14 and 16 of the evaporator which are located within the unit 43 are supplied with refrigerant from the compressor 56. The refrigerant preferably iscaused to ow through the coils or tubes of the second portion 16 of the evaporator and thence through the coils or tubes of the iirst portion 14 of the evaporator.

The air is caused to circulate through the unit 48, the air ducts 52 and 54 and the display space by the blower 1S embodiedV in the unit 43. The refrigerated air issuing fromthe cold air duct 54 ows downwardly about the.

articles arranged on the support or rack S0 so as to re rigeratethe same. At the same time, a portion of the refrigerated air flows substantially horizontally across` the upper portion of the display space to the return air duct 52 for return to the inletside of the unit 4S. In fact,l after the articles contained in the display space have been cooled to a temperature approaching that of the air being circulated, the major portion of the refrigerated Furthermore, the streamlining ot" air from the cold air duct 54 ows across the top of the display space in a manner to establish a moving air curtain vbetween the articles on display and the air above the display space.

The air passing to the return air duct 52 takes up moisture from the articles on display preventing them from becoming frosted up or freezing together. It also takes up and carries with it moisture received from the ambient air as customers reach into the case or as a result of diffusion of moist, warm air downward into the air curtain.

The temperature of the air flowing to the unit 48 through the return air duct after passage through the display space is, of course, higher than that of the air leaving the unit after refrigeration. It also hasa substantially increased moisture content as pointed out above. The blower 18, by its operation, serves to draw the return air downwardly from the display space and through the return air duct to the unit 48 so that upon contacting the coils and tins of the frost removing portion 14 of the unit, `its temperature is reduced and the moisture therein is largely deposited on the coils and ns of the first portion of the evaporator. The resulting partially refrigerated and dried air then passes to the blower but does not deposit moisture or frost on either the blower of the surfaces adjacent thereto. Therefore, the operation of the blower is not impaired in any way.

The blower vigorously agitates the air and forces it over and between the closely spaced fins 26 of the second portion 16 of the evaporator and the temperature of the air is thereby reduced materially. However, but little or no additional moisture is extracted from the air or deposited on the coils and fins of the second portion of the evaporator. The latter portion of the evaporator therefore does not tend to become clogged withfrost and remains in a high state of efficiency throughout its operation.

The turbulence of the air created by operation of the blower is substantially suppressed by the passage of the air between the closely positioned ns 26 of the evaporator portion 16 and as a result, the air issuing from the discharge side 12 of the unit 48 is substantially streamlined in its flow. It then travels up the cold air duct S4 adjacent the front wall of the case with a minimum of agitation and turbulence and a minimum of heat transfer or loss through the wall of the case. Moreover, it is unnecessary to employ the screens, deilectors or air distributing means which are normally required to create such streamlined flow and assure uniform distribution of the air throughout the length of the case. The air therefore enters the top of the display space at a temperature closely approximating that at which it leaves the unit 48 and travels smoothly across the display space with a minimum of agitation and pick up of heat and moisture from the ambient atmosphere.

The advantages attained by the use of the unit of Figs. 1 and 2 in a self-service refrigerated display case are of particular importance in those cases employed for low temperature operation such as that required for the refrigeration and display of ice cream. The temperatures preferably employed in such cases are from l0 to 20 degrees below zero and under such circumstances, the air being circulated should be maintained at a temperature of from 2O to 30 degrees below zero. However, these temperatures so closely approach that of the refrigerant being circulated that the eiciency of the evaporator employed and of the heat exchange effected must be very high. The advantages of the present invention are therefore of great importance. It is also found in practice that the length of time required to defrost the evaporator and the length of time required to restore the air to its original low temperature is materially reduced. The duration of the defrost cycle required in most selfservice ice cream cases of the prior art is in the neighborhood of 2 hours, whereas defrost cycles of only l hour to' an hour'and a quarter have been found satisfactoryV the portion 14 is generally larger than the portion 16y for the reason -that the latent heat which must be absorbed in order to condense and freeze the moisture contained in the air is much greater than that which must be absorbed in reducing the sensible heat of the air. The portions of the evaporator are ordinarily connected in series so that the refrigerant will ow from one to the other end and preferably from the second portion of the evaporator to the first portion thereof. However, the direction of refrigerant flow may be reversed and,'if desired, the evaporator portions need not be connected together at all, but each may be supplied with refrigerant from a separate compressor. The temperature at which the evaporator portions are maintained may also be quite different and may be varied as required for any particular installation or conditions of operation encountered in the equipment to be refrigerated.

When the evaporator-blower assembly is used in a walk-in cooler for the storage of meats and other produce. it may be positioned as shown at -60 inFig. 4 adjacent the top of the cooler 62 and arranged to circulate air from the front toward the rear of the cooler. In such installations, moisture laden air entering the cooler upon opening the door 64 is rapidly drawn into the unit 60 so as to flow over the frost collecting portion of the evaporator before it has an opportunity to diffuse throughout the cooler to deposit moisture on the articles in storage. However, the unit 60 may, of course, be positioned in any other desired location for effectively reducing the temperature of the air in the space under refrigeration.

The form, construction and arrangement of the evaporator-blower unit and of the elements thereof shown in Figs. 1 and 2 are preferred in that they permit the fabrication of the assembly in a compact and standardized form of general application. However, the evaporator portions and the blower may be constructed and mounted separately in the equipment in various positions adapted to assure substantial defrosting of the air in the first portion of the evaporator and eiective reduction in temperature of the relatively dry and turbulent air leaving the blower. Furthermore, while the assembly is of particular value in producing and maintaining low temperatures in refrigerated equipment, it may also be used to advantage in refrigerated vegetable and dairy cases, air conditioning systems and elsewhere.

It should therefore be understood that the particular embodiments and application of the invention shown in the drawings and described above are intended to be illustrative only and are not intended to limit the scope of the invention.

I claim:

l. An evaporator-blower unit for operation at temperatures below freezing, comprising top and bottom plates arranged in generally parallel relation, side members connected to said top and bottom plates and cooperating therewith to define an air duct having an inlet end and an outlet end, a blower located in said air duct, said blower being mounted on a supporting plate extending generally parallel to said top and bottom plates, a bafe extending from said supporting plate to the top plate adjacent the blower for directing air from said inlet end of the air duct to the intake side of the blower, a baliie on the opposite side of said blower extending from the supporting plate to the bottom plate for directing air from the outlet side of the blower to said outlet end of the air duct, a first evaporator coil located in said 'sie dueeeeweem the .brewer and. meiner end of the, air

duct; a` second evaporator coillocated in thek air duct between saidblowerzand the outlet end of the air duct, saidblower being, `operable* to draw air through said inlet ende of. the' air duct and over thefirst evaporator coil and to =force air over the second: evaporator coil and through saidoutlet: end of the air duct, said evaporator coilshaving nsthereon extending generally parallel to the direction of ow'of the air through the airv duct, the tins on thezrst evaporator coil being positioned farther apart than the ns on thek second evaporator coil.

2.A Anevaporator-blower unit for operation at. temperatures below freezing, comprising top and bottom plates arrangedk ine generally parallel relation, side members connected. to said top and bottom. plates and cooperating therewith-to define an air duct having an inlet end and an outlet end, a. blower located in said air duct, said blower beingl mounted yon a supporting plate extending generally parallel to said` top and bottom plates, a baille extending from said supporting plate to the top plate adjacent the blower for directing air from said inlet end of. the air duct to the intake side of the blower, a bafile on the opposite side of said blower extending from the supporting plate to` the bottom plate for directing air from the outlet sideof the;b1owerjtosaid, outlet, end': oit;

the air: duct, a; iirst. evaporator coilalocated.. in. said:aix.f

duct between the blower and. the inlet end of'. the: air.-

duct, a second evaporator coil located in the airduct: between` saidblower and the outlet' end of thev air duct,

said blower being operable tov draw air through said inlet end. of. the air duct and. over the rst evaporator coil, and to forcev air over the second evaporator coil` and,

through said outlet end of the air duct, saidv evaporator4 coils. having; ns thereon. extending generally parallel. to the direction of ow of the air through the air duct, said first evaporator coil being relatively larger than the, second evaporator coil and the fins on the rst evaporator coil being` positioned farther apart than the -tins on the.y

second evaporator coil.

References Cited in the le of this patent,

UNTED STATES PATENTS Bishop Feb. 23 1954" 

